/**
 * 直方图比较：compareHist()
 * 1. Correlation ( CV_COMP_CORREL )
 * 2. Chi-Square ( CV_COMP_CHISQR )
 * 3. Intersection ( method=CV_COMP_INTERSECT )
 * 4. Intersection ( method=CV_COMP_INTERSECT )
 */

#include "opencv2/imgcodecs.hpp"
#include "opencv2/imgproc.hpp"
#include <iostream>

using namespace std;
using namespace cv;

const char *keys =
        "{ help  h| | Print help message. }"
        "{ @input1 | base_0.jpg | Path to input image 1. }"
        "{ @input2 | test_1.jpg | Path to input image 2. }"
        "{ @input3 | test_2.jpg | Path to input image 3. }";

int main(int argc, char *argv[]) {
    //! [Load three images with different environment settings]
    CommandLineParser parser(argc, argv, keys);
    Mat src_base = imread(parser.get<String>("@input1"));
    Mat src_test1 = imread(parser.get<String>("@input2"));
    Mat src_test2 = imread(parser.get<String>("@input3"));
    if (src_base.empty() || src_test1.empty() || src_test2.empty()) {
        cout << "Could not open or find the images!\n" << endl;
        parser.printMessage();
        return -1;
    }
    //! [Load three images with different environment settings]

    //! [Convert to HSV]
    Mat hsv_base, hsv_test1, hsv_test2;
    cvtColor(src_base, hsv_base, COLOR_BGR2HSV);
    cvtColor(src_test1, hsv_test1, COLOR_BGR2HSV);
    cvtColor(src_test2, hsv_test2, COLOR_BGR2HSV);
    //! [Convert to HSV]

    //! [Convert to HSV half]
    Mat hsv_half_down = hsv_base(Range(hsv_base.rows / 2, hsv_base.rows), Range(0, hsv_base.cols));
    //! [Convert to HSV half]

    //! [Using 50 bins for hue and 60 for saturation]
    int h_bins = 50, s_bins = 60;
    int histSize[] = {h_bins, s_bins};

    // hue varies from 0 to 179, saturation from 0 to 255
    float h_ranges[] = {0, 180};
    float s_ranges[] = {0, 256};

    const float *ranges[] = {h_ranges, s_ranges};

    // Use the 0-th and 1-st channels
    int channels[] = {0, 1};
    //! [Using 50 bins for hue and 60 for saturation]

    //! [Calculate the histograms for the HSV images]
    Mat hist_base, hist_half_down, hist_test1, hist_test2;

    calcHist(&hsv_base, 1, channels, Mat(), hist_base, 2, histSize, ranges, true, false);
    normalize(hist_base, hist_base, 0, 1, NORM_MINMAX, -1, Mat());

    calcHist(&hsv_half_down, 1, channels, Mat(), hist_half_down, 2, histSize, ranges, true, false);
    normalize(hist_half_down, hist_half_down, 0, 1, NORM_MINMAX, -1, Mat());

    calcHist(&hsv_test1, 1, channels, Mat(), hist_test1, 2, histSize, ranges, true, false);
    normalize(hist_test1, hist_test1, 0, 1, NORM_MINMAX, -1, Mat());

    calcHist(&hsv_test2, 1, channels, Mat(), hist_test2, 2, histSize, ranges, true, false);
    normalize(hist_test2, hist_test2, 0, 1, NORM_MINMAX, -1, Mat());
    //! [Calculate the histograms for the HSV images]

    //! [Apply the histogram comparison methods]
    for (int compare_method = 0; compare_method < 4; compare_method++) {
        double base_base = compareHist(hist_base, hist_base, compare_method);
        double base_half = compareHist(hist_base, hist_half_down, compare_method);
        double base_test1 = compareHist(hist_base, hist_test1, compare_method);
        double base_test2 = compareHist(hist_base, hist_test2, compare_method);

        cout << "Method " << compare_method << " Perfect, Base-Half, Base-Test(1), Base-Test(2) : "
             << base_base << " / " << base_half << " / " << base_test1 << " / " << base_test2 << endl;
    }
    //! [Apply the histogram comparison methods]

    cout << "Done \n";
    return 0;
}
